Use of streaming media technology (e.g. video over Internet Protocol (IP) and voice over IP) is growing across all market segments, inclusive of consumer, enterprise, and public safety. There are numerous adjustable parameters which a modern digital video encoder uses to determine a level of overall video compression (characterized by an encoded bit rate and thereby a decoded video quality level) applied to source video, namely: encoded spatial resolution, encoded frame rate, and encoded spatial compression (which is typically a function of the quantization factor applied to transformed spatial data). The amount of throughput or bandwidth required for a given stream is largely a function of the values chosen for these three parameters. Typically, the encoded bit rate of a video stream is constrained by the underlying network connecting the source to the receiver. This is particularly true when that underlying network is wireless in nature.
For consumer applications of video streaming (e.g. video telephony, video-on-demand), it may be acceptable to statically fix the parameters iterated above for a given target bit rate. For a given video application (e.g. video telephony), the “mission” of the user receiving video (e.g. engage in a conversation) is unlikely to change.
Within the context of public safety applications, however, it may be advantageous to dynamically vary video compression parameters dependent on the mission of the user receiving video. For example, a field officer, not currently assigned to an incident, may be routinely monitoring surveillance video from other incidents in progress in the event he or she is later assigned to one of these incidents. The encoded quality of this video is likely to be normally low in such instances to minimize the impact on wireless system resources. This lowered level of quality is perfectly acceptable for the officer's mission immediately at hand: to remain situationally aware. Now assume the officer is assigned, by way of a Computer Aided Dispatch, or CAD system, to one of these incidents; clearly, his mission has significantly changed. Among other objectives realized with this change in the officer's disposition, the assigned officer may need to now perform recognition on one or more objects or persons depicted in the received video. These activities will require a relatively higher level of encoded video quality.
Similarly, a fixed camera may provide surveillance video of the inside of a bank which is presently being robbed. The video stream from the camera may be transmitted to responding officers. While these officers are en route to the bank, there may be little value in transmitting to them a relatively high level of encoded video quality (and consequently a relatively high encoded bit rate) given that they are focused on driving safely and preparing for their response. During their commute, a lowered level of encoded video quality is likely acceptable to provide basic situational awareness while minimizing the impact on wireless system resources. Once the officers arrive on scene and with their vehicles safely parked, it may be advantageous to significantly increase the encoded video quality such that the responding officers can engage in a strategic decision making process based on surveillance video. This activity will require a relatively higher level of encoded video quality.
Thus, there exists a need for a method and apparatus for adjusting video compression parameters for encoding source video based on a viewer's environment or disposition.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.